As known, these suspension bridges are highly exposed to winds, the effects of which have to be taken into account--in many respects--when planning the bridge. The present invention particularly concerns the effects produced by crosswind pressure, which tends to cause a horizontal inflection of the bridge framework, thereby creating remarkable stresses especially in correspondence of the point of anchorage of said framework to the end piers supporting the bridge.
It is also known, in fact, that this area of the bridge framework is subject to stresses, which become higher--on the one hand--the wider the span of the bridge, and--on the other hand--the longer the distance of the bridge lateral edges from its central axis.
In a bridge--for instance like that described in EP-A-0,233,528, filed by the same Applicant--having a span wider than 3 Km and a transversal verse dimension of about 50 m, the stresses in correspondence of the point of anchorage of the framework to the end piers can become inadmissible.
Hereinafter, reference is made to a bridge framework formed of a fixed stiff branch--corresponding to the framework part extending from the pier axis towards the embankment--and of a flexible branch, corresponding to the framework part extending from the pier axis towards the central bay. Of course, this assumption is quite arbitrary since, in real fact, no part of the bridge framework can be considered totally fixed and stiff; nevertheless, it helps to better understand the invention and define its contents in a conventional way.